Estrogen

Estrogen

Estrogen is probably the most widely known and discussed of all hormones. The term "estrogen" actually refers to any of a group of chemically similar hormones; estrogenic hormones are sometimes mistakenly referred to as exclusively female hormones when in fact both men and women produce them. However, the role estrogen plays in men not entirely clear.

In order to understand the role estrogens play in women, it is important to understand something about hormones in general. Hormones are vital chemical substances in humans and animals. Often referred to as "chemical messengers," hormones carry information and instructions from one group of cells to another. In the human body, hormones influence almost every cell, organ and function. They regulate our growth, development, tissue function, sexual function, the way our bodies use food, the reaction of our bodies to emergencies, and even our moods.

The estrogenic hormones are uniquely responsible for the growth and development of female sexual characteristics and reproduction in both humans and animals. The term "estrogen" includes a group of chemically similar hormones: estrone, estradiol (the most abundant) and estriol. Overall, estrogen is produced in the ovaries, adrenal glands and fat tissues. More specifically, the estradiol and estrone forms are produced in the ovaries, while estriol is produced by the placenta during pregnancy.

In women, estrogen circulates in the bloodstream and binds to estrogen receptors on cells in targeted tissues, affecting not only the breast and uterus, but also the brain, bone, liver, heart and other tissues.

Estrogen controls growth of the uterine lining during the first part of the menstrual cycle, causes changes in the breasts during adolescence and pregnancy, and regulates various other metabolic processes, including bone growth and cholesterol levels.

During the reproductive years, the pituitary gland in the brain generates hormones that cause a new egg to be released from its follicle each month. As the follicle develops, it produces estrogen, which causes the lining of the uterus to thicken.

Progesterone production increases after ovulation in the middle of a woman's cycle to prepare the lining to receive and nourish a fertilized egg so it can develop into a fetus. If fertilization does not occur, estrogen and progesterone levels drop sharply, the lining of the uterus breaks down and menstruation occurs.

If fertilization does occur, estrogen and progesterone work together to prevent additional ovulation during pregnancy. Birth control pills (oral contraceptives) take advantage of this effect by regulating hormone levels. They also result in the production of a very thin uterine lining, called the endometrium, which is unreceptive to a fertilized egg. Plus, they thicken the cervical mucus to prevent sperm from entering the cervix and fertilizing an egg.

Oral contraceptives containing estrogen may also relieve menstrual cramps and some perimenopausal symptoms, and regulate menstrual cycles in women with polycystic ovarian syndrome (PCOS). Furthermore, research indicates that birth control pills may reduce the risk of ovarian, uterine and colorectal cancer.